1. Field of the Invention
The present invention relates to a light modifier, used in photography, and more specifically to a light modifier equipped with a frosted fresnel lens, fitted into an all-plastic housing employing longitudinally adjustable combined modeling/strobe light source.
2. Background of the Invention
One of the most important aspects of photography is the ability to control light.
There are two primary artificial lighting techniques used in professional photography: constant light source, or electronic strobe. Of these two methods, the strobe light has gained prominence as the preferred method. This light source is designed for use with films balanced for daylight.
The exposure times for daylight films are generally of short duration, ranging from 1/10 second to 1/10,000 second. This is ideal for situations where fast shutter speeds or short bursts of intense light are required to capture the action or expression. In addition, the strobe light can be mixed with available daylight either as the main source or a filler.
Contemporary studio lighting calls for a strobe light fitted with a relatively low intensity modeling light, around or adjacent to the flash tube. The purpose of the modeling light is for viewing the desired lighting effect, and for focusing and composing. When the camera shutter is tripped, the strobe light is triggered in synchronization with the shutter, and the film is exposed. It is this more powerful strobe light which actually exposes the film.
A typical combined modeling/strobe light source, may be mounted on a variety of reflectors and light modifiers. Most common are simple parabolic reflectors of varying focal lengths and configurations. They generally have polished or dull surfaces designed to direct the light beam. Several designs of "soft boxes" and "bounce umbrellas" are also employed to create a diffused, softer light.
In the "soft box" version the light source is placed inside a fabric box whose framework is usually made of lightweight tubing. It typically has a black, light-tight rear and side panels, and a white, translucent front surface. In the "bounce umbrella" arrangement, the light is pointed into the underside of the umbrella and reflected back into the area to be illuminated. These lights are generally used for broad, soft illumination.
Another method of light control is the so-called theatrical or spot light. In this application the light is installed inside a metal housing, fitted with a heat absorbing fresnel type glass lens. A focusing mechanism allows the light to traverse longitudinally. By moving the light closer to the lens the light beam spreads; conversely, backing the light away from the lens condenses it to a spot.
This design has been used in both still and cinema photography and theatrical productions, essentially unchanged, for the past century. The metal housing is usually equipped with elaborate baffles and venting arrangements in an attempt to get rid of the high heat build-up, and to protect the operator from burns. The light source employed is typically of the tungsten type which uses a high wattage light bulb.
While it is possible to modify this existing technology for still photography, the heavy metal housing, or the heavy fresnel glass, is no longer required or desirable. This old-style spot light has several distinct disadvantages in its present configuration:
The heavy metal construction of the housing, necessary to support the thick glass fresnel lens, makes it cumbersome to transport and handle. To compound the problem, the yoke assembly has to be made correspondingly heavier, to support the weight of the housing.
If accidentally dropped, the glass lens breaks easily.
Because of its weight, the metal light modifier has to be mounted on a heavier, more expensive stand. These motion picture studio stands are not generally found in still photography.
For cosmetic reasons, and to prevent rusting, the metal housing requires a painted finish, inside and out; moreover, it scratches and dents easily.
Sheet metal construction presents severe design limitations, both esthetic and practical, especially for a cylindrical shape design.
Typical glass fresnel lenses have two or three facets per inch, and have a fairly thick cross section. The bulk of the glass between the reflective surfaces has no effect on the optical properties of the lens, however, it will affect the light output due to absorption loss, resulting in less light output for a given light source. Moreover, the widely spaced facets create disturbing, uneven, hot spots and rings on the object being illuminated.
The combination of glass lens and the labor intensive method of manufacturing the metal light housing, results in a very expensive unit. The above cited factors are basically responsible for the limited use of this otherwise excellent light source, by still photographers.
Because the strobe light has become the preferred method of lighting, several attempts have been made to convert the existing tungsten powered theatrical lights for use with a strobe light. However, with the advent of the modern high output flash and low wattage modeling lights, the heat build-up is no longer a problem, hence, there is no reason why both the housing and the lens cannot be replaced with a lightweight, lower cost, plastic components.
Development of an adjustable light modifier, rotatable 360 degrees vertically and horizontally, which is lighter in weight, has a thinner lens, can be easily handled and supported and which does not project rings and hot spots would represent a significant improvement in the field of photographic lighting and would satisfy a long felt need of the studio and location photographers.